Acquisitions, Dispositions and Other Significant Transactions - Ventas Lease Portfolio Restructuring (Details)		3 Months Ended		12 Months Ended
	Apr. 26, 2018 USD ($) community extension_option	Mar. 31, 2019 USD ($) lease	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) community	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Apr. 26, 2019 USD ($)	Jan. 01, 2019
Business Acquisition [Line Items]
Number of communities leased | lease		251
Loss on facility lease termination and modification, net		$ 209,000	$ 0
Ventas, Inc | Master Lease And Security Agreement
Business Acquisition [Line Items]
Number of communities leased | community	128
Prior number of communities | community	107
Additional number of communities | community	21
Number of communities added to agreement | community				17
Number of extensions | extension_option	2
Extension term	10 years
Rent expense				$ 175,000,000
Rent credit				8,000,000
Rent credit after change of control				$ 5,000,000
Base rent escalator, CPI increase									2.25%
Operating leases, base rent escalator, cpi increase multiplier									4
Base rent escalator, CPI decrease									0.00%
Investment minimum, unit per lease	$ 2,000
Period of lease	24 months
Investment maximum requirement to investment, period	36 months
Investment in capital improvements	$ 30,000,000
Payment for change of control fees	$ 25,000,000
Management percent fee				5.00%
Loss on facility lease termination and modification, net				$ 125,700,000
Forecast | Ventas, Inc | Master Lease And Security Agreement
Business Acquisition [Line Items]
Rent credit					$ 5,000,000	$ 7,000,000	$ 8,000,000
Option to terminate, annual base rent								$ 30,000,000
Option to terminate, rent reduction percentage								6.25%